An assessment of the NetAtmo weather station

This post is also available in: Spanish

Five months ago (september 2013) I installed an NetAtmo weather station in my family´s house in Ontinar (Zaragoza).


In practice, it consist on three aluminium cylinders with similar dimensions of a soda can (45x45x155 mm the biggest one) as the ones at right, that I placed in different points of the house and with which I can get these measurements:

  • room and outdoor temperature in ranges between -40 to 65°C, with a +/- 0.3°C accuracy;
  • humidity from 0 to 100% with a +/-3% accuracy;
  • barometric pressure in ranges between 260 to 1160 mbar, with a +/-1 mbar accuracy;
  • carbon dioxide concentration in a range between 0 to 5000 ppm (parts per million) with a +/- 50 ppm or +/-5% accuracy;
  • noise in a range between 35 dB to 110 dB;
  • air quality index taking into account the most important pollutants: particulate matter (PM10 and PM2.5), nitrogen dioxide (no2), ozone (o3), carbon monoxide (co) and sulphur dioxide (so2). These data are not measured by the station itself but it receives them from the european project CITEAIR (Common Information to European Air).

The station also displays the weather forecast issued by MeteoGroup.

I can access all this information whenever and wherever I am with an Internet connection or cellular data coverage, through an interface looking like this:


Grading: Medio-high performance

If I´d had to grade the station 0 to 10, it could be close to 8 taking into account the following factors, which are the station´s most useful features for me:

  • Design: 10;
  • Performance: 10;
  • CO2 sensor calibration: 3;
  • Measurement accuracy: 6;
  • Interface: 10;
  • Support and software updates: 8;

Carbon dioxide sensor calibration

A medium-high grade is not bad, but one of the key station´s features which persuade me was the CO2 measurement. You will notice that this is one of the aspects to assess and fails clearly: 3.

The CO2 sensor calibration system lacks, directly, technical solvency. The optical sensor measuring CO2 calibrates considering that the lowest CO2 level all around the globe is 400 ppm,  regardless of the location. This is incorrect.

I made contact NetAtmo staff to clarify this point. They treated very correctly my request but they finally recognized that the station meets technical constraints impeding a CO2 calibration according to the real CO2 level in every location and that the only technical possibility was to establish the most representative value available, the data measured at Mauna Loa Island in Hawaii.

So, regardless the place where the station is installed, the sensor will calibrate considering that the minimum CO2 level is 400 ppm, being this value much more higher in many locations along the globe.

The less bad news is, despite my village´s air may be more polluted than an island in the Pacific Ocean, air quality is good. When the CO2 sensor calibrates, his default value 400ppm won’t be very different to the real value. It may be useful for me.

Measurement accuracy

Other factor decreasing the station´s overall grading is the measurement accuracy, 6. The temperature sensor in one of the modules displays values exceeding the accuracy range +/- 0.3°C. Maybe two degrees.

I´d get it again

Despite the untrustworthy calibration system of the CO2 sensor and the deviation in the values in one of the temperature sensors, the station is fantastic. The interface to check the information is delight: functional, estable, fast and pleasant.

The station got several awards, very well-deserved

This is not the kind of device I´d trust if I´d had to go to Chernobyl and it´d measure atomic radiation, but this is perfect to know the weather as a citizen.

Medium.high performance.

12 thoughts on “An assessment of the NetAtmo weather station”

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  2. Hi, I’m curious why you think having the CO2 sensor, which I think is a K30, simply assume the lowest value it observes over a certain interval of time equals 400 ppm is “incorrect.” This seems reasonable to me. Sure there are differences in atmospheric CO2 around the globe (97 “active sites” are listed here I just checked 3 stations randomly:

    USH (Argentina): 393-399 ppm 2014
    SEY (Seychelles): 394-399 ppm in 2014
    TAP (Tae-han Peninsula, Korea): 387-427 ppm in 2014

    And yes there are differences every day.

    But don’t you think one value of such an inexpensive, near-real-time CO2 sensor is to remind us, as Santorio Santorio discovered 400 years ago, that we exhale CO2? And those concentrations in my own home can reach >1000 ppm, an increase over background of 600 ppm, eclipsing the annual range for both Argentina and Seychelles and being 15 times greater than even TAP’s annual difference of 40 ppm.

    Here in the US, the Netatmo’s come with an outdoor module and an additional indoor module. Only the indoor modules measure CO2, not the outdoor modules. This could be because the K30 sensor inside is not sufficiently sensitive to monitor outdoor changes in CO2 concentration. But I think (and will soon test) it does a great job tracking indoor changes in CO2!

    Thank you for posting this and for all your work to build what I call carbon literacy. I’m not sure how to translate it but ¿maybe alfabetización de carbono?

    1. Hi Tony,

      I agree with you in that in most of locations around the globe, the Netatmo station is reasonably accurate for an “user level”. I don´t really mind if the CO2 concentration outdoors my village´s house is 400 or 420ppm.

      But, think in crowded and polluted cities where the concentration levels easily exceed the 600ppm peak and the 500ppm mean concentration.

      In these cases, we are talking of mismatches of more than 200ppm compared to the 400ppm considered as reference level of the Netatmo station. These figures may be relevant. If i´d live in Delhi or Beijing instead of my village, the CO2 measures should´t be so convincing.

      Anyway, when it strictly comes to human health, CO2 concentrations are still far from causing serious damages

      The bad news is the trend….

      More than “alfabetización”, which is to lear to write and speak, “bibliografía sobre carbono” or “literatura sobre el carbono” sounds better 🙂



  3. I really have doubts about the accuracy of the CO2 measurements. I my home, the station sometimes give values below 300 ppm, and during the night in the bedroom it rises above 3000 ppm. That is really high value of CO2.

    1. In my case the range of CO2 values never were lower than 400ppm, and the max. levels are about 2000ppm. But the station´s CO2 sensor is one of the aspects that deserve more improvement.

    2. thats the actual value of the netatmo: in can detect such high concentrations which actually happen indoor and are unhealthy!

  4. Thank you for this very interesting post !
    I was looking for the real accuracy of this sensor because the CO2 concentration in the bedroom of my son is regularly above 1500ppm during the night (and goes done the 400ppm when we ventilate our home).
    As you mention, I was also surprised about this calibration. If you don’t ventilate your home and the concentration is still around 800ppm, then after calibration, this will become a ‘false’ good air assessment !

    About the problem of calibration with the 400ppm concentration outside, Netatmo could either use your location to assess the concentration outside (if you leave in the downtown of a city or in the country side) or could use the external module… The first can be applied without any modification of the material, just a post calibration of online data.

  5. Did you try changing the calibration of temperature measurement? I guess you would need an accurate temperature to do that. It’s under advanced options.

  6. My netatmo shows 25 ppm CO2.
    After calibration it went to 400, then to 1000 when I was cooking… and then to 250 ppm 🙂

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